1. Field of the Invention
This invention relates to inhibited, hydroxypropylated blends of starches which are capable of imparting desirable rapid heat penetration and good texture to food products, particularly to puddings, when the foods are cooked at super atmospheric pressure.
2. Brief Description of the Prior Art
Starch has long been used as a thickener for many types of foods. In recent years as the use of prepared and processed foods has become more prevalent, a demand has arisen for foods having properties specially adapted to the requirements of industrial processing. In response to this demand, specially modified starches, capable of imparting to food products these required special properties, have come into use. A particularly useful type of modified starch for the food industry is one having "thin-thick" properties. Such a starch does not develop appreciable viscosity when cooked in boiling water at normal atmospheric pressure, but does develop appreciable viscosity after cooking under pressure (retorting). Starches having "thin-thick" properties are useful in the canning industry when thickened canned foods are to be prepared. When canned foods containing such a starch as a thickening agent are heated in a bath having a temperature between 240.degree. and 300.degree.F., the heat can penetrate rapidly into the unthickened contents of the can to raise the internal temperature of the contents above 212.degree.F. The contents of the can are thus rapidly sterilized. Upon cooling, the cooked starch must thicken in order for the food product in the final form to possess a desired viscosity and texture.
Starches suitable for use under such retorting conditions have been prepared from both corn and high amylose corn; however, none of the retort starches developed heretofore possessed all the necessary properties required for certain end uses. Specifically, retort starches prepared from inhibited corn starch such as those described in U.S. Pat. Nos. 3,422,088 and 3,804,828 have good heat penetration but have relatively low end viscosities after retort so may be unsuited for use in certain food systems; while the degree of inhibition may be decreased in order to raise the end viscosity, this procedure results in poor heat penetration. Retort starches prepared using high amylose products, particularly high amylose corn starch such as those described in co-pending U.S. patent application Ser. No. 317,413 filed Dec. 21, 1972 now U.S. Pat. No. 3,904,601 have also been found to be unsatisfactory for use in certain food systems. In many food systems containing high amounts of natural fats, e.g. chicken gravy, these high amylose starches form complexes with the fats thus decreasing viscosity to an extent such that it has been found necessary to use larger quantities of starch to effect suitable thickening. In other food systems, e.g. pudding, the high amylose starches have been found to produce good viscosity but the final products are noticeably poor in such textural properties as mouth feel.
There is thus a need in the art for a retort starch which will produce food products having a combination of good heat penetration, high end viscosity after retort, good texture and mouth feel.
It is therefore an object of the present invention to provide novel starch blends having properties useful in retorted canned foods. It is a further object of the invention to provide starch blends which do not develop significant viscosity when cooked at retort temperatures, do not develop significant viscosity when cooled to about 120.degree.F., after retorting but do develop significant viscosity when cooled to room temperature after retorting.